Castings of aluminium alloys



Patented 6, 1938 UNITED STATES PATENT OFFICE CASTINGS F ALLOYS PaIulSpitaler, Bitterteld, Germany, assignmto FarbenindustrieAktiengesellschait,

Frankiort-on-the-Main, Germany No Drawing. Application April 24, 1935,Serial No. 17,971. In Germany May 3 Claims.

rectly with the magnesium content of the alloy,

the higher themagnesium content, the larger being the amount of siliconneeded to produce the desired eflect. On the other hand, however, higherpercentages of silicon result in a considerable lowering of the strengthand elongation of the alloys, so that, in order to obtain castings whichwill meet the usual commercial requirements in this respect, theaddition of silicon .to alloys high in magnesium must remain below theoptimum amounts for the attainment of compact texture. Bearing theseconditions in mind, alloys that have been found suitable are thosecontaining between about 4 and about 7% of magnesium and between about0.8 and 1.5% of silicon (the latter increasing within the specifiedlimits, with the magnesium content of the alloy). A very suitable alloyis one containing of magnesium and 1 to 1.2% of silicon. Manganese, inamounts up to 2.5% (preferably about 1%) may also be incorporated withthe alloy.

It has also been observed that the siliceous alloys described above arenotably superior, in respect also of their strength at hightemperatures, to the corresponding alloys containing either no siliconat all, or such amountsof silicon, i. e. not more than about 0.3%, asare normally M present as impurity, inasmuch as, at higher temperatures,the tensile strength of the alloys diminishes to a less extent than thatof the corresponding alloys free from silicon. For example, when analloy containing 5% of magnesium, 1.1%

I of silicon and 0.1% of manganese, is heated to about 300 0., itstensile strength is only about 25% lower than at room temperature,whereas, inthecase oithesame alloy, containing only 0.2%

of silicon, the strength at 300 C. is already more than 35% lower.

This observation-probably ail'ords at least a partial explanation of themore compact texture of the castings made from the siliceous alloys,since, owing to the greater strength of these alloys at the highertemperatures through which they pass after solidification, the looseningof their structure is correspondingly slighter.

Castings made of the following aluminium alloys show the describedqualities:

1. 5.0% Mg (2.) 7.0% Mg (3. 5.0 Mg

- 2.0 Si 0.3 Mn

1%: Si 1.5%, Si

4. 5.0 M s. '4. M a. a. M

Even castings with comparatively thin walls (for example about 5 mm.)made from alloys in accordance with the invention, are practically quiteimpervious under a positive pressure of at least 8 atmospheres.

- As the result of their greater compactness of texture, in conjunctionwith their known property of resisting corrosion, the alloys of thepresent invention are suitable for the production of a great variety ofmould castings, such as fittings for pipes conveying liquids,carburetter parts, hydraulic control members, compressor casings,vessels for containing liquids and gases, and the like.

I claim: l 1. Castings of an aluminium alloy. containing of magnesium.1.1% of silicon and 0.1% of manganese, balance aluminium having acompact texture and a high mechanical strength.

2. Castings of aluminium alloys consisting of 5 to 7% of magnesium, 0.8to 1.5% of silicon, manganese in a quantity up to 2.5% the balance beingaluminium, such castings having a compact tex- 'ture and a highmechanical strength at elevated temperatures.

3. .Castings of aluminum alloys consisting ofabout 5% of magnesium,between about 1.0 and about 1.2% of silicon, up to 1% of manganese, thebalance being aluminium, such castings having a compact texture and ahigh mechanical strength at elevated temperatures.

, PAUL BPITALER.

